1. FIELD OF THE INVENTION
The present invention relates to the field of grip and hold structures which can be used in conjunction with a lifting and moving apparatus such as a forklift to physically lift and move large slabs of concrete and other heavy objects and in particular to remove poured concrete slabs from their location so that underlying structures become accessible.
2. DESCRIPTION OF THE PRIOR ART
In general, various types of apparatus used in conjunction with lifting and moving objects are known in the prior art. Applicant is aware of the following prior art patents which disclose various embodiments of apparatus used for lifting and moving.
1. U.S. Pat. No. 4,194,868 issued to Walker et al. in 1980 for "Valve Lifting Attachment For Fork Lift" discloses a lifting attachment for a forklift to enable the forklift to lift a plurality of heavy water valve assemblies. The device consists of an elongated beam to which is attached a multiplicity of chain and hook members to lift the valve assembly.
2. U.S. Pat. No. 4,087,947 issued to Turner in 1978 for "Edge-Lifting System For A Concrete Slab" discloses a lifting attachment to a concrete slab which must be inserted while the concrete is still wet after it has been poured. The apparatus is not functional for use with a hard concrete slab.
3. U.S. Pat. No. 3,552,583 issued to Toffolon in 1971 for "Panel Erection Apparatus" relates to a panel erection apparatus for lifting various types of panels. An integral portion of the apparatus requires that the frame members of the panel be exposed for gripping.
4. U.S. Pat. No. 3,499,676 issued to Haeussler in 1970 for "System For Manipulating Concrete Bodies" relates to an apparatus for moving concrete slabs which includes a ball and socket arrangement attached to an anchor bolt.
5. U.S. Pat. No. 3,264,026 issued to Hansen in 1966 for "Hook Attachment For A Fork Lift Vehicle" discloses a chain and hook member for lifting an article wherein the lifting member can be used in conjunction with the prongs of a forklift.
6. U.S. Pat. No. 3,229,836 issued to Koenig in 1966 for "Cement Sack Pallet And Handling Equipment" discloses a pallet for moving sacks of cement where the pallet has tunnels for receiving the prongs of a forklift.
7. U.S. Pat. No. 3,180,513 issued to Vander Wal in 1965 for "Attachment For Fork-Lift Trucks" discloses a pair of metal receiving member which are used to lift a wooden pallet. The receiving members are hingeably attached to the wooden pallet, so that it may be tipped by appropriate movement of the forklift prongs relative to the pallet.
8. U.S. Pat. No. 2,735,563 issued to Kelly in 1956 for "Running Board Handling Attachment For Lift Trucks" discloses an embodiment of a freight car running board lifting and handling device for use with a forklift.
9. U.S. Pat. No. 2,690,271 issued to Marietta in 1954 for "Attachment For Lift Trucks" discloses a specialized lifting attachment to be attached to the prongs of a forklift.
10. U.S. Pat. No. 2,589,342 issued to Christensen in 1952 for "Lift Truck Accessory" relates to an attachment to a forklift which permits the forklift to handle and dump the contents of large crates.
As can be seen from the above referenced prior art patents, previously known devices have the capability of lifting a preformed slab of concrete or panel member before it is installed in its final form. The lift means requires the ability to be able to grip an internal member (as in the Toffolon Patent) or alternatively requires that lifting means be inserted into the concrete while it is still wet and before it has hardened (as in the Turner Patent).
What is not known in the prior art is an apparatus by which a poured and hardened concrete slab which has been set in its final position on the ground may be picked up and safety moved to another location so that the area beneath the slab becomes accessible. The poured and affixed concrete slab is already hardened, and therefore it is not possible to set gripping means comparable to that disclosed in the Turner patent. Since the concrete slab only has the smooth upper surface (and possibly smooth sidewalls) exposed, there are no exposed beams for attachment by the apparatus in Toffolon. The system in Haeussler is unstable and provides no protection in the event the anchor bolt should sheer loose from the concrete slab due to the strain of its weight or the motion imparted to it.
Therefore, a significant need exists for an apparatus which can be securely attached to poured and hardened concrete which is in place on the ground and which can be used in conjunction with a lifting and moving means such as a forklift to lift and move the concrete slab so that the ground under the slab is exposed.